In U.S. Pat. No. 4,121,584 of Turner, et al., a technique for the positive control of flow of parenteral solution or the like is provided, utilizing only the gravity head pressure of the solution, coupled with excellent accuracy of delivery volume. The flow control device utilizes a pair of alternating valves which open and close, controlling the inlet and outlet of a metering chamber.
In the patent application of Nicholas Zissimopoulos, Ser. No. 878,970, filed Feb. 17, 1978, an improved system is disclosed for a flow control device, utilizing the principles disclosed in the Turner, et al. patent. Specifically, a separable casette defining a fluid flow path through it and having valvable inlet and outlet means is provided for temporary installation in a controller. The controller provides means for valving the inlet and outlet in the manner desired for administering a predetermined flow volume of fluid through the casette.
Accordingly, the casette may be part of a disposable solution administration set, while the controller constitutes permanent equipment.
As shown in the cited patent and application, the valving means comprises a pair of plungers, as part of the controller, which penetrate apertures in the casette and press a membrane against the walls of orifices at the inlet and the outlet of a metering chamber. This provides reliable metering of liquid through the casette.
Since the casette should be installed in the controller with the plungers penetrating through apertures into the casette, the above-cited patent application provides mechanical means for installation of the casette into its proper position. This is accomplished by sliding the casette into a holding bracket which precisely positions it, and then rotating a crank which moves the casette laterally into engagement with the plungers.
While the previously described device permits the reliable engagement of the casette into its proper position, it is desirable for a clear visual and/or auditory alarm signal to be provided to indicate the proper engagement of the casette, to avoid any remote possibility of the apparatus being inoperative during use because of the accidental failure to properly move the casette laterally into completely engaged position by use of the crank.
In accordance with this invention, such an alarm system is provided so that a visual and sound indication may be provided at all times during operation of the apparatus if the casette is not in its fully engaged position with the plungers.